Methods and systems for analyzing samples

Abstract

This disclosure relates to a method for analyzing a sample of material. The method includes (a) converting a portion of the sample into a plasma multiple times; (b) recording a spectrum of electromagnetic radiation emitted in response to each of the sample conversions to define a sequence of spectra for the sample, in which each member of the sequence corresponds to the spectrum recorded in response to a different one of the sample conversions; (c) using an electronic processor to compare the sequence of spectra for the sample to a sequence of spectra for each of at least one reference sample in a reference library; and (d) using the electronic processor to determine information about the sample based on the comparison to the reference samples in the library.

What is claimed is: 
     
       1. A method for analyzing a sample, the method comprising:
 converting a portion of the sample into a plasma multiple times; 
 recording a spectrum of electromagnetic radiation emitted in response to each of the sample conversions to define a sequence of spectra for the sample, wherein the sequence of spectra for the sample comprises multiple members, and each member of the sequence corresponds to the spectrum recorded in response to a different one of the sample conversions; 
 using an electronic processor to compare the sequence of spectra for the sample to a sequence of spectra for each of at least one reference sample in a reference library, wherein the sequence of spectra for each reference sample comprises multiple members, and the comparing comprises comparing the number of times each member occurs in the sequence of spectra for the sample with the number of times each member occurs in the sequence of spectra for each reference sample; and 
 using the electronic processor to determine information about the sample based on the comparison to the at least one reference sample in the library. 
 
     
     
       2. The method of  claim 1 , wherein a pulse of electromagnetic radiation is used to convert the sample into the plasma for each of the multiple times. 
     
     
       3. The method of  claim 2 , wherein members of the sequence for the sample correspond to the spectra recorded in response to different parameters for the pulse of electromagnetic radiation used to convert the portion of the sample into the plasma during the multiple times. 
     
     
       4. The method of  claim 3 , wherein the different parameters comprise different pulse energies, different pulse durations, different pulse wavelengths, or combinations thereof. 
     
     
       5. The method of  claim 2 , wherein members of the sequence for the sample correspond to the spectra recorded in response to different incident locations on the sample for the pulse of electromagnetic radiation used to convert the portion of the sample into the plasma during the multiple times. 
     
     
       6. The method of  claim 5 , wherein the different incident locations are separated sufficiently to characterize heterogeneity in the atomic composition of the sample. 
     
     
       7. The method of  claim 5 , wherein the different locations are separated from one another by at least 10 μm. 
     
     
       8. The method of  claim 5 , wherein the different incident locations comprises at least 10 different locations. 
     
     
       9. The method of  claim 2 , wherein members of the sequence for the sample correspond to the spectra recorded in response to combinations of different parameters for the pulse of electromagnetic radiation used to convert the portion of the sample into the plasma during the multiple times and different incident locations on the sample for the pulse of electromagnetic radiation used to convert the portion of the sample into the plasma during the multiple times. 
     
     
       10. The method of  claim 2 , wherein members of the sequence for the sample correspond to the spectra recorded in response to the pulse of electromagnetic radiation used to convert the portion of the sample into the plasma during the multiple times that has a fixed spectral delay. 
     
     
       11. The method of  claim 1 , wherein the conversion of the sample into the plasma causes the sample to emit electromagnetic radiation indicative of atomic emissions. 
     
     
       12. The method of  claim 1 , wherein the conversion of the sample into the plasma causes the sample to emit electromagnetic radiation indicative of one or more of isotopic emissions, molecular emissions, molecular isotopic emissions, and spectral interference between atomic emissions from different atoms in the sample. 
     
     
       13. The method of  claim 1 , wherein each spectrum is recorded with a spectral resolution sufficient to resolve the emission of electromagnetic radiation corresponding to atomic emission and one or more of isotopic emission, molecular emission, molecular isotopic emission, and spectral interference between atomic emissions from different atoms. 
     
     
       14. The method of  claim 1 , wherein each spectrum is measured with a spectral resolution finer than 0.1 nm. 
     
     
       15. The method of  claim 1 , wherein each spectrum is measured over a range including from 195 nm to 1005 nm. 
     
     
       16. The method of  claim 1 , wherein the sequence of spectra for the sample comprises members corresponding to all of the different spectra recorded for the sample during the multiple times. 
     
     
       17. The method of  claim 16 , wherein the comparison by the electronic processor comprises comparing a probability distribution for the members of the sequence of spectra for the sample being analyzed to a probability distribution for members of the sequence of spectra for each of the reference samples. 
     
     
       18. The method of  claim 17 , wherein the probability distribution for the sample being analyzed is represented as a histogram indicating the number of times each member occurs in the sequence of spectra for the sample being analyzed and the probability distribution for the members of each reference sample is represented as a histogram indicating the number of times each member occurs in the sequence of spectra for each reference sample. 
     
     
       19. The method of  claim 1 , wherein the comparison by the electronic processor comprises identifying a degree to which the sequence for the sample matches a sequence for each of the at least one reference sample in the library. 
     
     
       20. The method of  claim 19 , wherein identifying the degree to which the sequence for sample matches a sequence for each of the reference samples comprises comparing a probability distribution for the members of the sample being analyzed to a probability distribution for members of the sequence of spectra for each of the reference samples. 
     
     
       21. The method of  claim 19 , wherein identifying a degree comprises:
 comparing each spectrum in the sequence for the sample to the different spectra in the library to identify the different spectra from the library most likely to match the spectra in the sequence for the sample; 
 identifying which reference samples from the library comprise all of the identified spectra; and 
 identifying a degree to which the sequence for the sample matches a sequence for each of the identified reference samples. 
 
     
     
       22. The method of  claim 1 , wherein the reference library is made by:
 providing information about the identity of each reference sample; 
 converting a portion of each reference sample into a plasma multiple times; and 
 recording a spectrum of electromagnetic radiation emitted from each reference sample in response to each of the reference sample conversions to define a sequence of spectra for each reference sample, wherein each member of the reference sample sequence corresponds to the spectrum recorded in response to a different one of the reference sample conversions. 
 
     
     
       23. The method of  claim 22 , wherein members of each reference sample sequence correspond to the spectra recorded in response to combinations of different parameters for a pulse of electromagnetic radiation used to convert the portion of each reference sample into the plasma during the multiple times and different incident locations on each reference sample for the pulse of electromagnetic radiation used to convert the reference sample into the plasma during the multiple times. 
     
     
       24. The method of  claim 1 , wherein the at least one reference sample comprises multiple reference samples. 
     
     
       25. The method of  claim 24 , wherein the multiple reference samples comprises metal alloys having common elemental compositions and different processing protocols. 
     
     
       26. The method of  claim 1 , wherein the sample being analyzed and the reference sample comprise metal alloys having a common elemental composition, and wherein the information determined by the electronic processor is whether the sample being analyzed has been subjected to a specific processing protocol corresponding to one of the reference samples. 
     
     
       27. The method of  claim 1 , wherein the information about the sample comprises an identity for the sample. 
     
     
       28. The method of  claim 1 , wherein the information about the sample comprises a provenance for the sample. 
     
     
       29. A system for analyzing a sample, the system comprising:
 an excitation source for converting a portion of the sample into a plasma multiple times; 
 a spectrometer configured to record a spectrum of electromagnetic radiation in response to each of the sample conversions to define a sequence of spectra for the sample, wherein the sequence of spectra for the sample comprises multiple members, and each member of the sequence corresponds to the spectrum recorded in response to a different one of the sample conversions; and 
 an electronic processor configured to compare the sequence of spectra for the sample to a sequence of spectra for each of at least one reference sample in a reference library and determine information about the sample based on the comparison to the at least one reference sample in the library, wherein the sequence of spectra for each reference sample comprises multiple members, and the comparing comprises comparing the number of times each member occurs in the sequence of spectra for the sample with the number of times each member occurs in the sequence of spectra for each reference sample.